Portion of a shoe midsole



FIG. 1 is a perspective view of portion of a shoe midsole showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof; and,

FIG. 4 is a left side elevational view thereof.

The phantom line showing environment is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for portion of a shoe midsole, as shown and described. 